Disk device and method of manufacturing disk device

ABSTRACT

According to one embodiment, a disk device includes a disk-shaped recording medium, a head which processes data on the recording medium, and a housing accommodating the recording medium and the head. The housing includes a base with a side wall, and a cover having a welded portion welded to the side wall by laser welding. The welded portion includes a first welded portion welded to a first region of the side wall and having weld beads with a first shape, and a second welded portion welded to a second region of the side wall and having welded beads with a second shape different from the first shape.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/264,889, filed Feb. 1, 2019, which is a continuation of U.S.application Ser. No. 15/995,834, filed Jun. 1, 2018, which is acontinuation of U.S. application Ser. No. 15/683,974, filed Aug. 23,2017, which is a continuation of Ser. No. 15/459,697, filed Mar. 15,2017 which claims the benefit of Provisional Application No. 62/382,897,filed Sep. 2, 2016, the entire contents of each are incorporated hereinby reference.

FIELD

Embodiments described herein relate generally to a disk device and amethod of manufacturing the disk device.

BACKGROUND

As a disk device, a magnetic disk drive is known, which comprises ahousing including a base and a top cover and accommodating therein arotatable magnetic disk and an actuator which supports a magnetic head.Further, such a method of improving the performance of a disk drive hasbeen proposed, that the housing is sealed with a low-density gas such ashelium so as to reduce the rotation resistance of the magnetic disk andthe magnetic head.

In such a magnetic disk drive, the top cover is jointed to the base ofthe housing by laser welding to form an enclosed housing and increasethe airtightness of the housing. The laser welding is carried out onalong an entire outer circumference of the top cover. Here, in order toobtain high airtightness, it is necessary to maintain a stable weldingquality all around the circumference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an appearance of a hard disk drive(HDD) according to the first embodiment.

FIG. 2 is an exploded perspective view of the HDD according to the firstembodiment.

FIG. 3 is a perspective view showing a base of a housing of the HDD.

FIG. 4 is an expanded perspective view of a region D in FIG. 3.

FIG. 5 is a cross section of the HDD taken along line V-V in FIG. 1.

FIG. 6 is a cross section of the HDD taken along line VI-VI in FIG. 1.

FIG. 7 is a flowchart illustrating a manufacturing process for the HDD.

FIG. 8 is a plan view schematically showing an example of a processingstep in the manufacturing process.

FIG. 9 is a perspective view schematically showing a welded portion ofthe housing in a processing step.

FIG. 10 is diagram showing a first laser irradiation condition and asecond laser irradiation condition in a welding step.

FIG. 11 is a diagram showing a welded portion of a housing of an HDDaccording to the second embodiment, and a first laser irradiationcondition and a second laser irradiation condition in a welding step.

FIG. 12 is a perspective view schematically showing a part of the weldedportion 50 of the outer cover 16 in the second embodiment.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings. In general, according to one embodiment, a diskdevice includes a rotatable discoidal recording medium, a head whichprocesses data on the recording medium and a housing accommodating therecording medium and the head and a cover including a welded portionjoined to the base by laser welding. The welded portion includes a firstwelded portion formed under a first laser irradiation condition and asecond welded portion formed under a second laser irradiation conditiondifferent from the first laser irradiation condition. As examples of amagnetic disk device, hard disk drives (HDD) according to embodimentswill now be described in detail.

First Embodiment

FIG. 1 is a perspective view showing the appearance of an HDD accordingto a first embodiment, and FIG. 2 is an exploded perspective viewshowing an internal structure of the HDD.

As shown in FIGS. 1 and 2, the HDD comprises a flat and substantiallyrectangular housing 10. The housing 10 comprises a rectangularbox-shaped base 12 an upper surface of which is opened, an inner cover14 screwed to the base 12 with a plurality of screws 13 to close theopening of the upper end of the base 12, an outer cover (top cover) 16overlaid on the inner cover 14 and including a circumferential portionwelded to the base 12. The base 12 includes a rectangular bottom wall 12a opposes the inner cover 14 with a gap therebetween and side walls 12 bprovided to stand along with the periphery of the bottom wall, which aremolded into one body with, for example, aluminum. The side wall 12 bincludes a pair of long side walls 13 a opposing each other and a pairof short side walls 13 b opposing each other. On upper end surfaces ofthe side walls 12 b, a substantially rectangular frame-shaped fixing rib12 c is provided to project therefrom. The inner cover 14 is formedfrom, for example, stainless steel into a rectangular plate. Thecircumferential portion of the inner cover 14 is screwed to the uppersurfaces of the side walls 12 b of the base 12 with the screws 13, andthus fixed to an inner side of the fixing rib 12 c. The outer cover 16is formed from, for example, aluminum into a rectangular plate. Theouter cover 16 has dimensions slightly larger than those of the innercover 14. The circumferential portion of the outer cover 16 is welded tothe fixing rib 12 c of the base 12 over its entire circumference, to beairtightly fixed. The welded structure will be described in detaillater.

Vents 46 and 48 to communicate the outside and inside of the housing 10with each other are formed in the inner cover 14 and the outer cover 16,respectively. The air in the housing 10 is discharged through the vents46 and 48 and then a low-density gas (inert gas) having a density lowerthan that of air, for example, helium is introduced through the vents 46and 48 and enclosed or sealed in the housing 10. For example, a seal(sealing member) 52 is stuck on the outer surface of the outer cover 16so as to close the vent 48.

As shown in FIG. 2, the housing 10 accommodates therein a plurality ofmagnetic disks 18 as recording media and a spindle motor 20 as a drivesection, which supports and rotates the magnetic disks 18. The spindlemotor 20 is placed on the bottom wall 12 a. Each of the magnetic disks18 is formed to have a diameter of, for example, 88.9 mm (3.5 inches)and include a magnetic recording layer on the upper and/or lower surfacethereof. The magnetic disks 18 are engaged coaxially with a hub (notillustrated) of the spindle motor 20, and are clamped with a clampspring to be fixed to the hub. Thus, each magnetic disk 18 is supportedand situated to be parallel to the bottom wall 12 a of the base 12. Eachmagnetic disk 18 is rotated at a predetermined number of revolutionswith the spindle motor 20.

Note that five magnetic disks 18 are accommodated in the housing 10 inthis embodiment as shown in FIG. 2, but the number of magnetic disks 18is not limited to this. Or a single magnetic disk 18 may be accommodatedin the housing 10.

The housing 10 accommodates therein a plurality of magnetic heads 32which write/read data on/from the magnetic disks 18, a head stackassembly (actuator) 22 which supports the magnetic heads 32 movably withrespect to the magnetic disks 18. The housing 10 further accommodatestherein a voice coil motor (to be referred to as VCM) 24 which rotatesand aligns the head stack assembly 22, a ramp load mechanism 25 whichretains the magnetic heads 32 in an unload position away from themagnetic disks 18 when the magnetic heads 32 moved to the outermostcircumference of the magnetic disks 18, and a board unit 21 on whichelectronic components including a conversion connector and the like aremounted.

The head stack assembly 22 comprises a rotatable bearing unit 28, aplurality of arms 30 extending from the bearing unit 28, and a pluralityof suspensions 34 extending from the respective arms 30, and a magnetichead 32 is supported on a distal end of each suspension 34.

A printed circuit board (not shown) is attached to an outer surface ofthe bottom wall 12 a of the base 12. The printed circuit board 25controls operations of the spindle motor 20, and also the VCM 24 and themagnetic heads 32 via the substrate unit 21.

FIG. 3 is a perspective view showing the base 12 of the housing 10 whenthe structural elements are removed. FIG. 4 is a perspective view of anarrow portion of the base. FIG. 5 is a cross section of the housingtaken along line V-V in FIG. 1. FIG. 6 is a cross section of the housingtaken along line VI-VI in FIG. 1. As shown in FIGS. 3 and 4, therectangular frame-shaped fixing rib 12 c is integrally provided on theupper end surfaces of the side walls 12 b of the base 12. The rib 12 cis formed in its most part as a first region (broad portion) 30 a havinga first width W1. At least a part of the rib 12 c, in this embodiment,there are three second regions (narrow portion) 30 b having a secondwidth W2 less than the first width W1. Of the three second regions 30 bof the rib 12 c, two are located on the right and left long side walls13 a located adjacent to the outer circumference edge of the respectivemagnetic disk 18, and one is located at the central portion of one shortside wall 13 b. The side surface of each second region 16 b on amagnetic disk 18 side is concaved into a shape of an arc along the outercircumference edge of the magnetic disk 18.

As shown in FIGS. 1, 5 and 6, the circumferential portion of the outercover 16 is welded to the rib 12 c of the base 12, thus forming arectangular frame-shaped welded portion 50 formed along its entirecircumference. The welded portion 50 includes a first welded portion 50a laser-welded to the first region 30 a of the rib 12 c under a firstlaser irradiation condition, which will be described later, and threesecond welded portions 50 b welded to the second regions 30 b of the rib12 c, respectively, under a second laser irradiation condition differentfrom the first laser irradiation condition.

Next, a method of manufacturing the HDD configured as above, a weldingmethod and a welded structure will be described. FIG. 7 is a flowchartschematically illustrating an example of the manufacturing process, andFIG. 8 is a plan view schematically showing an example of the weldingprocess for the HDD.

As shown in FIG. 7, first, the spindle motor 20, the magnetic disk 18,the head stack assembly 22 and other structural components areincorporated and installed on the base 12 of the housing 10 in, forexample, a clean room (ST1). Then, the inner cover 14 is put on the base12 and fixed to the base 12 with the screws 13 to close the opening ofthe base 12 (ST2).

Further, after installing the outer cover 16 to be overlaid on the innercover 14 (ST3), the housing 10 is set on an XY table 60 as shown in FIG.8. The XY table 60 is movable in the X direction and the Y directionperpendicularly intersecting therewith by a driver source (not shown). Alaser beam irradiation device (light-emitting optical head) 62 isprovided above the XY table 60. The laser beam irradiation device 62irradiates a laser beam onto a predetermined position of the outer cover16 of the HDD to regionally fuse the rib 12 c of the base 12 and theouter cover 16 and weld the outer cover 16 to the rib 12 c (ST4). By thewelding, the outer cover 16 is regionally fused and solidified to formweld beads (welded portion 50) on an outer circumferential portion ofthe outer cover 16.

In the welding process, a laser beam is irradiated to thecircumferential portion of the outer cover 16 by the laser beamirradiation device 62 while moving the housing 10 in the direction of Xand the Y direction as required with the XY table 60, and thus thecircumferential portion of the outer cover 16 is subjected to laserwelding continuously all around its circumference.

As shown in FIG. 7, it is judged in the welding process whether or notthe region to which the outer cover 16 is to be welded is the firstregion 30 a of the rib 12 c of the base 12 (ST5), and if it is the firstregion 30 a, the laser beam is irradiated onto the outer cover 16 underthe first laser irradiation condition (ST6) to be welded. Under firstlaser irradiation condition, the irradiation position is set for weldingthe outer cover 16 to the first region 30 a of the rib 12 c so that thelaser beam is irradiated to the central portion of the rib 12 c in thewidth W1 direction as shown in FIG. 5.

As shown in FIG. 7, it judged as not the first region 30 a to weld inST5, then is further judged whether or not the region to weld is thesecond region 30 b of the rib 12 c (ST7). If judged that it is thesecond region 30 b, the laser beam is irradiated onto the outer cover 16under the second laser irradiation condition different from the firstlaser irradiation condition to weld the outer cover 16 to the secondregion 30 b of the rib 12 c (ST8). Under the second laser irradiationcondition, the irradiation position is set for welding the outer cover16 to the second region 30 b of the rib 12 c so that the laser beam isirradiated onto the central portion of the rib 12 c in the width W2direction as shown in FIG. 6. In other words, in the second laserirradiation condition, the distance from an outer edge of the rib 12 cto the laser irradiation position is set shorter than the distance fromthe outer edge of the rib 12 c to the laser irradiation position in thefirst laser irradiation condition. In the second laser irradiationcondition, the laser irradiation position is shifted towards the outeredge side of the rib 12 c as compared to the laser irradiation positionin the first laser irradiation condition.

FIG. 9 is a perspective view schematically showing a part of the weldedportion 50 of the outer cover 16. FIG. 10 is a diagram showing anexample of each of the first and second laser irradiation conditions inlaser welding.

As shown in FIGS. 9 and 10, under the first laser irradiation condition,the outer cover 16 is laser-welded continuously at a constant laseroutput (continuous irradiation) and a constant laser scanning speed A.Under the second laser irradiation condition, two items, namely, thelaser output waveform and the laser scanning speed are changed. Morespecifically, under the second laser irradiation condition, the laserbeam is irradiated in pulses by repeatedly switching the laser output onand off while fixing a laser scanning speed B constant and greatlyslower than the laser scanning speed A in the first laser irradiationcondition. Thus, the first welded portion 50 a of the outer cover 16 isformed to contain belt-shaped weld beads which continuously extend inthe scanning direction of the laser beam by the continuous irradiationof the laser beam. The second welded portions 50 b are formed bystacking a plurality of circular weld beads welded by the pulseirradiation of the laser beam in order.

Then, as shown in FIG. 7, it judges whether or not the all-aroundwelding of the entire circumferential portion of the outer cover 16 iscompleted (ST9), and if not, ST5 to ST8 described above are repeatedlycarried out. In this manner, the outer circumferential edge of the outercover 16 is continuously laser-welded to the first region 30 a of therib 12 c and the three second regions 30 b, and when the all-round outercircumferential edge of the outer cover 16 has been welded, the weldingprocess is finished. Thus, the circumferential portion of the outercover 16 can be laser welded in its entire circumferences without a gap.

Note that this embodiment employs the method of scanning the outer cover16 by a laser beam while moving the housing 10 with the XY table 60, butit is not limited to this. For example, the laser beam irradiationdevice 62 may be moved for scanning while fixing the housing 10 still.Moreover, in the welding step, the first welded portion 50 a and thesecond welded portion 50 b are continuously laser-welded, but it isalternatively possible that first, only the entire first welded portion50 a is laser-welded and then the three second welded portions 50 b arelaser-welded in order.

As shown in FIG. 7, in the manufacturing process of the HDD, after thelaser welding of one round of the circumferential portion is completed,the air in the housing 10 is exhausted through the vents 46 and 48(ST10), and further, through the vents 46 and 48, a low density gas(inert gas) having a density lower than that of air, for example,helium, is introduced in the housing 10 (ST11) to be enclosed or sealedtherein. Then, the seal 52 is stuck on the surface of the outer cover 16to close the vent 48 (ST12). By the above-discussed processing steps, anenclosed type HDD containing a low-density gas inside is obtained.

According to the magnetic disk device having the above-describedstructure and its manufacturing method, the laser irradiation conditionis changed according to the rib width, or more specifically, the firstlaser irradiation condition is used for the case where the outer coveris laser-welded to the first region having a great rib width, and it ischanged to the second laser irradiation condition for laser-welding theouter cover to the second region having a less rib width. Thus, anappropriate laser welding is carried out for each of the rib widths, andtherefore a stable welding quality can be obtained all around thecircumference of the welded portion of the outer cover. According tothis embodiment, in the second laser irradiation condition, the laseroutput is not fixed constant, but made in pulses and also the laserscanning speed is significantly reduced. In this manner, the welding iscarried out while repeating a melting and a solidifying in each andevery spot of the laser irradiation, and therefore a high weldingquality can be secured even in the second regions 30 b which have a lessrib width. A total zone of the second regions 30 b having a less ribwidth is much shorter than the first region 30 a, and therefore even ifthe laser scanning speed is reduced 1/10, the effect on the totalwelding time is small.

Moreover, the first region 30 a and the second region 30 b of the rib 12c are subjected to laser welding under different laser irradiationconditions, and therefore it is not necessary to match the rib width ofthe first region 30 a with that of, i.e. a less width of the secondregion 30 b, thereby making it possible to form the first region 30 a tohave a greater rib width than conventional cases. In this manner, thewidth of the portion to be welded to the first region 30 a can beincreased, thereby making it possible to improve the welding quality andairtightness. Or even if the rib width of the first region 30 a is thesame as the conventional ones, and the second region 30 b has a narrowrib, a stable welding quality can be obtained.

As described above, according to this embodiment, it is possible toobtain a disk drive having a high welding quality and an improvedairtightness, and its manufacturing method.

Now, an HDD and its manufacturing method according to another embodimentwill be explained. In the following explanation of the other embodiment,those elements that are the same as those in the first embodiment willbe given the same reference numbers and their detailed explanation willbe omitted or simplified. Those elements that are different from thefirst embodiment will be mainly explained in detail.

Second Embodiment

FIG. 11 is a diagram showing a part of the HDD according to the secondembodiment, an example of each of the first and second laser irradiationconditions in laser welding, and FIG. 12 is a perspective viewschematically showing a part of the welded portion of the outer cover16.

In this embodiment, under the first laser irradiation condition forwelding an outer cover 16 to a first region 30 a of a rib 12 c, a laseroutput is set at a fixed first level P1 (continuous irradiation),whereas under the second laser irradiation condition for welding to asecond region 30 b of the rib 12 c, the laser output is set at a secondfixed level P2 (continuous irradiation) lower than the first level P1,as shown in FIG. 11.

Thus, as shown in FIG. 12, the first welded portion 50 a of the outercover 16 is formed to contain belt-shaped weld beads which continuouslyextend in the scanning direction of the laser beam by the continuousirradiation of the laser beam. The second welded portions 50 b areformed to contain belt-shaped weld beads which continuously extend inthe scanning direction of the laser beam by the continuous irradiationof the laser beam, respectively. The weld beads of the second weldedportions 50 b have a second width less than a first width of the weldedbeads of the first welded portion 50 a.

When welding to the narrower second region 30 b, the laser output isthus reduced to decrease the amount of melting of the rib of the base.Thus, the second region 30 b of narrow rib can be well handled. Sincethe laser output is temporarily changed while welding the outer cover 16in its entire circumference all around, unstable factors may increase,but as compared to the entire circumference, the corresponding portions(the second regions 30 b) are very small or short. The merit which canenlarge almost the entire rib dominates over these unstable factors.

The combinations of the first and second laser irradiation conditionsare not limited to those discussed in the first and second embodimentsdescribed above, but various combinations which will now be provided arealso possible.

1) The first laser irradiation condition defines irradiation of a laserbeam in pulses and the pulse frequency is set to F1 (for example, 10Hz). The second laser irradiation condition defines irradiation of alaser beam in pulses and the pulse frequency is set to F2 (for example,50 Hz) higher than F1.

2) The first laser irradiation condition defines irradiation of a laserbeam in pulses and the pulse pitch is set to C1 (for example, 0.3 mm).The second laser irradiation condition defines irradiation of a laserbeam in pulses and the pulse pitch is set to C2 (for example, 0.1 mm)less than C1.

3) The first laser irradiation condition defines irradiation of a laserbeam in pulses and the diameter of a beam spot is set to D1 (forexample, φ0.4 mm). The second laser irradiation condition definesirradiation of a laser beam in pulses and the diameter of a beam spot isset to D2 (for example, φ0.2 mm) less than D1.

4) The first laser irradiation condition defines irradiation of a laserbeam in pulses and the focal depth of a beam spot is set to Z1 (forexample, 5 mm).

The second laser irradiation condition defines irradiation of a laserbeam in pulses and the focal depth of a beam spot is set to Z2 (forexample, 0 mm) less than Z1.

5) The first laser irradiation condition defines continuous irradiationof a laser beam and the scanning speed of the laser beam is set to S1(for example, 50 cm/s). The second laser irradiation condition definescontinuous irradiation of a laser beam and the scanning speed of thelaser beam is set to S2 (for example, 25 cm/s) slower than S1.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

Additionally, for example, the locations of the narrow rib portions inthe housing is not limited to those discussed in the above-providedembodiments, but the narrow ribs may be located at any other arbitrarypositions. The number of narrow rib portions is not limited to three,i.e., it may be set to one, two or four or more. The materials, shapes,sizes, etc., of the elements forming the disk drive may be variouslychanged as needed. In the disk drive, the number of magnetic disks andthat of magnetic heads may be increased or decreased as needed, and thesize of each of the magnetic disks may be selected from variousalternatives.

What is claimed is:
 1. A method of manufacturing a disk device, themethod comprising: placing a recording medium in a base of a housing;fixing an inner cover onto the base to close an opening of the base;placing an outer cover on the base to overlay the inner cover; andwelding a peripheral portion of the outer cover to the base sequentiallyfrom a point around to the point while controlling a welding conditionto a first welding condition or a second welding condition differentfrom the first welding condition, depending a section of the peripheralportion.
 2. The method of claim 1, further comprising exhausting thehousing through a vent of the outer cover, and filling the housing witha gas having a density lower than that of air after the welding.
 3. Themethod of claim 1, wherein the welding comprises welding a part of theperipheral portion of the outer cover to the base under the firstwelding condition, and welding another part of the peripheral portion ofthe outer cover to the base under the second welding condition differentfrom the first welding condition.
 4. The method of claim 1, wherein thewelding includes a laser welding comprising irradiating a laser beam onthe peripheral portion of the outer cover and controlling a laserradiation condition in accordance with welding portions of the outercover.
 5. The method of claim 4, wherein the laser welding compriseswelding a part of the peripheral portion of the cover to the base by alaser beam under a first laser irradiation condition, and weldinganother part of the peripheral portion of the cover to the base by alaser beam under a second laser irradiation condition different from thefirst laser irradiation condition.
 6. A method of manufacturing a diskdevice, the method comprising: placing a recording medium in a base of ahousing; fixing an inner cover onto the base to close an opening of thebase; placing an outer cover on the base to overlay the inner cover; andwelding a peripheral portion of the outer cover to the base sequentiallyfrom a point around to the point while controlling a welding conditionto a first welding condition or a second welding condition differentfrom the first welding condition, depending a section of the peripheralportion.